Popularity of IP (Internet Protocol) telephony (e.g. VoIP, video calls, etc) is increasing, and deployments of IP Telephony are correspondingly increasing in terms of number of subscribers and size of networks. The increasing number of subscribers using IP telephony for their day to day communication places increased load on network infrastructure, which leads to poorer voice quality owing to inadequate capacity or faulty infrastructure.
IP telephony places strict requirements on IP packet loss, packet delay, and delay variation (or jitter). In multi-site complex customer networks, there may be many WAN edge routers that interconnect many branches of an enterprise or of many small businesses managed by a service provider.
Probable causes of poor voice quality at the WAN edge router are Codec conversions, mismatched link speeds, and bandwidth oversubscription owing to number of users, number of links, and/or link speed. Each of these causes results in buffer overruns, leading to packet discards, which in turn degrades the quality of voice or service.